Integral wiring harness

ABSTRACT

A method of manufacturing a touch panel wherein a glass substrate is coated with a resistive layer; a pattern of conductive edge electrodes and a conductive wire trace pattern are applied to the resistive layer; the conductive edge electrodes are electrically isolated from the conductive wire traces; and a protective insulative border layer is applied over the edge electrodes and the wire traces. A touch panel which includes a glass substrate coated with a resistive layer on one surface thereof; a pattern of edge electrodes on the resistive layer; a wire trace pattern on the resistive layer; a trench in the resistive layer between the wire trace pattern and the edge electrode pattern; and a protective insulative border layer over the edge electrode pattern and the wire traces.

RELATED APPLICATIONS

This application is related to application Ser. No. 09/169,391 filedOct. 9, 1998 entitled TOUCH PANEL WITH IMPROVED LINEAR RESPONSE ANDMINIMAL BORDER WIDTH ELECTRODE PATTERN.

FIELD OF THE INVENTION

This invention relates to a touch screen panel with integral wiringtraces which eliminates the bulky and unreliable prior art externalwiring associated with touch screen panels and lowers the cost ofmanufacturing touch screen panel assemblies.

BACKGROUND OF THE INVENTION

Touch screen panels generally comprise an insulative (e.g., glass)substrate and a resistive layer disposed on the insulative substrate. Apattern of conductive edge electrodes are then formed on the edges ofthe resistive layer. The conductive electrodes form orthogonal electricfields in the X and Y directions across the resistive layer. Contact ofa finger or stylus on the active area of the panel then causes thegeneration of a signal that is representative of the X and Y coordinatesof the location of the finger or stylus with respect to the substrate.In this way, the associated touch panel circuitry connected to the touchpanel by wiring traces can ascertain where the touch occurred on thesubstrate.

Typically, a computer program generates an option to the user (e.g.“press here for ‘yes’ and press here for ‘no’”) on a monitor underneaththe touch screen panel and the conductive electrode pattern assists indetecting which option was chosen when the touch screen panel wastouched by the user.

The application referred to above relates to an improved edge electrodepattern on the resistive layer of the touch screen panel. The instantapplication relates to an improvement in the prior art wiring harnessesattached to the touch screen.

There are typically four insulated individual wires, each extendingalong and around the edges of the touch screen panel to each corner ofthe touch screen panel where the insulation is removed and the wire ishand soldered to a terminal electrode on the panel at each corner of thepanel.

One or more additional layers, usually tape, are often used to securethe wires to the edges of the panel and there may be an insulative layerbetween the wires and the edge electrodes of the panel to electricallyisolate the wires from the edge electrodes.

The problem with such prior art devices are numerous. The solder jointsare often not very reliable and create solder bumps on the smoothsurface. Moreover, the act of soldering the ends of each wire to thecorner electrodes can damage the electrodes or even crack the substrateof the touch panel. Also, this assembly process is labor intensive andhence costly.

To reduce noise, a noise shield may be place under the wires. Adequatenoise protection, however, may not always be possible. Also, theassembled touch screen panel does not have a finished appearance.Instead, the taped on wires are bulky and readily noticeable and detractfrom the appearance to the touch screen panel.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a touch screenpanel with integral wiring traces.

It is a further object of this invention to provide a touch screen panelwith integral wiring traces which is more reliable than prior art touchscreen panel assemblies.

It is a further object of this invention to provide a touch screen panelwhich has a more finished, neat, and low profile appearance.

It is a further object of this invention to provide a method ofmanufacturing a touch screen panel with integral wiring traces.

It is a further object of this invention to provide such a method ofmanufacturing a touch screen panel with integral wiring traces whicheliminates the possibility of damaging the corner electrodes of thetouch screen panel and which eliminates the possibility of damaging thetouch screen substrate.

It is a further object of this invention to provide such a method ofmanufacturing a touch screen panel with integral wiring traces which isless labor intensive and less costly than prior art methods.

It is a further object of this invention to provide a touch screen panelwith integral wiring traces and a protective coating over both the wiretrace pattern and the edge electrode pattern.

It is a further object of this invention to provide a method ofmanufacturing such a touch screen panel in which the conductive silverpaste of the edge electrode pattern and the wire trace pattern isco-fired with the protective coating thereby resulting in a cost andtime savings.

This invention results from the realization that a more reliable, lesslabor intensive, less costly, and more aesthetically pleasing lowprofile touch screen panel assembly can be effected by integral wiringtraces wherein the prior art individual wires are replaced with a wiretrace pattern deposited on the resistive layer of the touch screen panelright on the panel either by printing or by some other method and thenelectrically isolating the wire trace pattern from the edge electrodepattern by laser etching or some other technique.

This invention features a method of manufacturing a touch panel, themethod comprising coating a glass substrate with a resistive layer;applying a pattern of conductive edge electrodes to the resistive layerand applying a conductive wire trace pattern to the resistive layer andelectrically isolating, the conductive edge electrodes troth theconductive wire traces.

The conductive layer is typically a tin antimony oxide composition andthe lass substrate may be a soda lime glass composition.

The step of applying the pattern of conductive edge electrodes and thewire trace pattern typically includes screen printing silver/frit pasteoil the resistive layer in the form of the edge electrode pattern andthe wire trace pattern. The step of electrically isolating includesusing a laser beam to ablate the resistive material between the edgeelectrodes and the wire traces. The step of applying, a protectiveinsulative border layer usually includes screen printing an insulativecomposition over the edge electrodes and the wire traces. The insulativecomposition is preferably a lead borosilicate glass composition.

The panel is subjected to an elevated temperature in a first period oftime to burn off any organic material and then a dwell period at theelevated temperature to cure the electrodes and wire trace materials andto fuse the insulative border layer material.

The elevated temperature is typically between 500° C.-525° C., the firsttime period is approximately 5 minutes, and the dwell period isapproximately 2-3 minutes.

A touch panel in accordance with this invention includes a glasssubstrate coated with a resistive layer on one surface thereof; apattern of edge electrodes on the resistive layer; a wire trace patternon the resistive layer; a trench in the resistive layer between the wiretrace pattern and the edge electrode pattern to electrically isolate thewire trace pattern from the edge electrode pattern; and a protectiveinsulative border layer over the edge electrode pattern and the wiretraces.

The resistive layer may be a tin antimony oxide composition and theglass substrate may be a soda lime glass composition. The pattern ofedge electrodes and the wire trace pattern is preferably made of asilver/frit paste composition. The protective insulative border layer ispreferably formed from a lead borosilicate glass composition.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a schematic view of a prior art touch screen panel assembly;

FIG. 2 is a schematic view of the touch screen panel of the subjectinvention just before the edge electrode pattern and the wire tracepattern are screen printed on the resistive coating;

FIG. 3 is a schematic view of the touch screen panel of the subjectinvention after the edge electrode pattern and the wire trace patternare screen printed on the edges of the touch screen panel;

FIG. 4 is a side cut-away view of a portion of the touch screen panel ofthe subject invention showing how a wire trace is electrically isolatedfrom the electrodes of the edge electrode pattern;

FIG. 5 is another cross-sectional view of a portion of the touch screenpanel of the subject invention after the protective insulative borderlayer is deposited over the edge electrode pattern and the wire tracepattern;

FIG. 6 is a chart showing the preferred firing dwell times andtemperatures associated with manufacturing the touch screen panel of thesubject invention; and

FIG. 7 is a flow chart depicting the primary manufacturing stepsassociated with the method of making the touch screen panel assembly inaccordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Prior art touch screen panel 10, FIG. 1, includes substrate 12 whichusually includes an insulative layer (e.g., glass), a resistive layerover the primary working surface of the insulative layer, and a patternof conductive edge electrodes 14 and terminal electrodes, usually cornerelectrodes 16, on the resistive layer as is known in the art. There areadditional corner electrodes (not shown) one at each other corner 18,20, and 22 of the touch screen. The edge electrodes 14 repeat in somepredetermined patterned fashion along each edge 24, 26, 28, and 30 ofpanel 10.

Wires 32, 34, 36, and 38 extend to each corner electrode and with theirends stripped of insulation are soldered to the respective cornerelectrodes in order to generate the appropriate electrical field acrossthe working surface 40 of panel 10. So, for example, wire 32 extendsalong edges 24 and 26 of panel 10 to the corner electrode (not shown) atcorner 18; wire 34 extends along edge 24 of panel 10 to corner electrode16; wire 38 extends along edges 24 and 30 of panel 10 to a cornerelectrode (not shown) at corner 20; and wire 36 extends along edge 24 ofpanel 10 to a corner electrode (not shown) at corner 22. In some priorart embodiments, an insulative tape and then an insulated noise shieldlayer 44 may be laid between the wires and the edge electrodes and toelectrically isolate edge electrodes 14. A hole is then formed in theinsulative tape proximate each corner electrode as shown at 46 in orderto solder the ends of each wire to the appropriate corner electrode.Alternatively, the tape ends proximate each corner electrode. In otherembodiments, the wires are simply taped to the edges of panel 10. Instill other embodiments, tape layer 48 and/or a protective (e.g.,“Kapton”) tape layer 50 are placed over the wires. Insulated noiseshield layer 44 may be placed over the edge electrodes and under wires32, 34, 36, and 38.

In FIG. 1, the thickness and width of border layers 44, 48, and 50 aregreatly exaggerated for the purposes of illustration as is the thicknessof substrate 12. Actual touch screen panels are usually ⅛ inch thick orless and layers 44, 48, and 50 are substantially thinner than that butstill wires 32, 34, 36, and 38 make the completed assembly appearsomewhat bulky and unfinished.

Moreover, prior art touch screen panel 10 in some cases is not veryreliable because the solder joints between the individual wires and thecorner electrodes can fail. Further, the act of soldering the ends ofeach wire to the corner electrodes can damage the electrodes or evencrack the substrate of the touch screen panel. In addition, the assemblyprocess wherein the wires are soldered at their ends to the cornerelectrodes and taped to the edges of the panel is labor intensive andhence costly.

In the subject invention, however, the wiring and protective layer isintegrated as a part of the touch screen panel so that there are nobulky wires or layers of tape associated with the touch screen panel asis the case with the prior art.

Touch screen panel 48, FIG. 2 in accordance with this invention ismanufactured by applying a resistive coating 50, (e.g., tin antimonyoxide) by a vacuum sputter process to glass substrate 52 (e.g., a sodalime glass composition). Coating 50 is less than 1000 angstroms thickand substrate 52 is typically between 1-3 mm thick and 15 inches on adiagonal depending on the specific application.

Conductive edge electrode pattern 54, FIG. 3 is then screen printed onresistive coating 50 using a conductive silver frit paste. (DuPont 7713)and at the same time wire trace pattern 56 is screen printed onresistive coating 50 also using conductive silver/frit paste, step 100FIG. 7.

As shown in FIG. 3 wire trace 58 begins at junction 60 and extends alongthe edge of panel 48 to corner electrode 62 of edge electrode pattern54. Wire trace 64 similarly begins at junction 60 and extends along theopposite edge of panel 48 to corner electrode 66 of edge electrodepattern 54. Wire trace 68 begins at junction 60 and extend to cornerelectrode 70 and wire trace 72 begins at junction 69 and extends tocorner electrode 74 of edge electrode pattern 54. The height of eachwire trace is typically between 12-16 microns high and between 0.015″and 0.025″ wide. Junction 60 uniquely forms a single attachment locationfor the controller interface which creates the electrical field acrossthe touch screen.

Edge electrode pattern 54 may take the form of the pattern disclosed incorresponding application Ser. No. 09/169,391 or the forms disclosed inU.S. Patent Nos. 4,198.539; 4,293,734; or 4,371,746 hereby incorporatedherein by this reference. Typically the edge electrode pattern and thewire trace pattern occupy only about ⅜ in. on the edges of panel 48 andthus FIG. 3 is not to scale.

After a drying operation at 120° C. for 5 minutes to dry the silver/fritpaste, the next step in the process is to electrically isolate each wiretrace from the electrodes of the edge electrode pattern other than thecorner electrodes and, in cases where there are two or more adjacentwire traces, to electrically isolate them from each other, step 102,FIG. 7.

As shown in FIG. 4 laser 80 is used to ablate resistive coating 50 inthe area between wire trace 58 and edge electrode pattern 54 to a depthtypically corresponding to the top of glass substrate 52. In this way,wire trace 58 is electrically isolated from edge electrode pattern 54and a similar technique is used to isolate wire traces 58, 72, 68, and64 from each other wherever there are two or more traces and also fromthe edge electrodes of the edge electrode pattern adjacent each wiretrace.

In the preferred embodiment, a Q-switched YAG laser was used to form a0.008-0.010 inch wide trench 82 in resistive coating 50. The laser beamhad a wavelength of 1.06 microns, and the average power was 32 watts.Other ablation or etching processes may be used to provide electricalisolation and, in some cases, trench 82 need not extend completelythrough resistive coating 50 provided electrical isolation is provided(i.e., some or a little resistive material may remain).

In the next step, a protective insulative border layer, 86, FIG. 5 isdeposited over the wire traces and the edge electrode pattern fillingthe trenches between adjacent wires and the trenches between the wiretraces and the edge electrodes adjacent them. In another embodiment, theinsulative material is deposited only in the trenches between the wiretraces and the edge electrodes adjacent them.

In the preferred embodiment, step 104, FIG. 7, an insulative leadborosilicate glass composition (DuPont DG-150) is screen printed aboutthe border area of the touch panel over the wire trace pattern and theedge electrode pattern. The width of border layer 86, FIG. 5 istypically about ½ in. and has height of about 12 microns after firing.

After lead-borosilicate-glass layer 86 dries at 120° C. for 5 minutes(an optional step) it and the conductive silver/frit paste of the edgeelectrode pattern and the wire trace pattern are cured by firing,preferably at the same time in an infrared oven, step 106. FIG. 7.

During this firing step, the organic binders of the silver/frit pasteand the lead borosilicate glass layer must be allowed to escape theouter layer before the lead borosilicate glass layer fully cures toprevent voids and defects.

Accordingly, outgassing is allowed to occur before the peak temperaturein the infrared oven is reached whereupon the silver/frit paste is curedand the lead borosilicate glass fully fuses.

As shown in FIG. 6, the preferred firing profile consists of a ramp fromroom temperature up to 500° C.-525° C. in approximately 5 minutes inorder to complete the solvent evaporation and burn out the organicbinders in the thick film materials. The ramp is followed by a dwellperiod above 500° C. for 2-3 minutes to allow the frit glass to melt andthe silver to sinter. The substrate is the brought back to ambienttemperature. An additional firing profile may consist of a ramp fromroom temperature to 300° C. with a dwell period between 300-400° C. for6-19 minutes to provide additional time to burn out the organic bindersif required. This dwell period is followed by a second ramp to the peaktemperature of 500° C.-525° C. with little or no dwell period. Thesubstrate is then brought back to ambient temperature. Before firing, aseparate drying step is performed to evaporate the solvents in the thickfilm materials. The drying profile consists of a ramp to 120-135° C. fora dwell period of 2-6 minutes and then brought back to ambienttemperature. The insulative lead borosilicate glass layer advantageouslyprotects the wire traces and the edge electrodes and isolates then fromeach other. In the prior art, tape was used which was unsightly andoften peeled up which left the edge electrodes and the wire tracesunprotected. Moreover, by co-firing the paste of the edge electrodepattern and the wire traces, and the borosilicate glass protectivelayer, the separate firing steps of the prior art are eliminated.

After firing, a hard coat and/or an anti-microbial and/or ananti-scratch coatings may be applied to the active area of the touchpanel (and optionally over the protective border layer) by spraying,and/or dipping techniques step 108, FIG. 7 and then a wiring cable isattached to junction 60, FIG. 3, step 110, FIG. 7.

Although specific features of the invention are shown in some drawingsand not in others, this is for convenience only as each feature may becombined with any or all of the other features in accordance with theinvention. The words “including”. “comprising”, “having,”, and “with” asused herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments.

Other embodiments will occur to those skilled in the art and are withinthe following claims:

1-18. (canceled)
 19. A touch panel comprising: a resistive layerdisposed on a surface of a substrate; a pattern of edge electrodesdisposed on the resistive layer in a border area around the substrateperiphery; wire traces disposed on the resistive layer in the borderarea, the edge electrodes and wire traces separated by trenches in theresistive layer; and an insulative material disposed at least in thetrenches.
 20. The touch panel of claim 19, wherein the resistive layercomprises doped tin oxide.
 21. The touch panel of claim 19, wherein theborder area is no more than about ⅜ inches wide.
 22. The touch panel ofclaim 19, wherein the insulative material covers the wire traces. 23.The touch panel of claim 19, wherein the insulative material covers theedge electrodes.
 24. The touch panel of claim 19, further comprising ahardcoat covering the resistive layer.
 25. The touch panel of claim 24,further comprising an antimicrobial coating covering the hardcoat. 26.The touch panel of claim 24, further comprising a scratch resistantcoating covering the hardcoat. 27-31. (canceled)